Field of Invention
The present invention relates to a fabrication device for micro/nano probe ball tips of a 3-dimensional coordinate measuring machine, and more particularly to a fabrication and monitoring device of micro probe ball tips.
Description of Related Arts
Since late 1980s, microfabrication technology had been continuously improved, which promoted the rapid progress and development of micro-mechanical, micro-electromechanical systems (MEMS) and other emerging disciplines. Micromachines and MEMS devices appeared in large numbers. Because of their geometric feature sizes between tens of micrometers to a few millimeters, measurement uncertainty is required to reach tens of nanometers to hundreds of nanometers. As a result, high-precision measurement of micro device geometry sizes is especially important. Conventionally, there are two categories of widely used measuring instruments: firstly, non-contact measuring instruments such as white light interferometer, digital holographic microscopy, scanning probe microscopy, atomic force microscopy, and other surface nondestructive measurement devices. However, these methods are unable to measure the three dimensional sizes with high aspect ratio, such as deep holes, side walls, ramps and the like; secondly, contact measuring instruments, mainly micro/nano coordinate measuring machines.
In micro/nano coordinate measuring machine, high-precision probe system directly affects the accuracy of the results. The probe stylus consists of a probe shaft and a probe ball tip. Conventionally, the probe shaft and the probe ball tip are most commonly connected by adhesive. Generally, a hole is drilled on the probe ball, and then the probe shaft is glued inside the hole on the probe ball. However, the hole on the probe ball may lead to deformation when the probe ball is glued on a bolt, resulting in sphericity decrease. In order to ensure no deformation of the probe ball during assembly, conventional probe is manufactured by gluing the undrilled probe ball in a spherical cup holder. Meanwhile, the probe ball and the probe shaft are not coaxial, which will produce eccentric error, so accuracy is not high enough.
With the widespread of high-precision coordinate measuring machine, probe ball specifications have become an important factor of statistical error budget. Especially, when measured parts with high aspect ratio, a probe ball with a diameter of less than 100 microns are needed (wherein conventionally, commercially available probe balls of probes for 3-dimensional coordinate measuring machine are all larger than 300 microns).
Conventionally, micro probe ball tip fabrication methods are as follows: WEDG-OPED (wire electrode grinding—one pulse electro discharge), MicroEcm-OPED (micro-electrochemical etching—one pulse electro discharge), LBM (Laser thermal processing), capillary tip molding, and optical fiber melting. For WEDG-OPED, the smallest diameter of the probe ball is 40 um. For Micro Ecm-OPED, the smallest diameter of the probe ball is 30 um. For LBM, the smallest diameter of the probe ball is 19.69 um. For capillary tip molding, the smallest diameter of the probe ball is 3 mm. For optical fiber melting, the smallest diameter of the probe ball is 30 um. Sphericity and eccentricity of probe ball tips processed by conventional methods are all several microns, which is not able to meet the needs of high-precision measurements.